bl30: mailbox driver add unified error code [1/2]

PD#SH-18313

Problem:
Customer need add unified error code number on
mailbox driver for debug convenience

Solution:
Add unified error code number on mailbox driver
API

Verify:
A5_AV409

Change-Id: I04910679dbea062572290c8928717c8f06a80c7e
Signed-off-by: Yao Jie <jie.yao@amlogic.com>
diff --git a/rtc/rtc.c b/rtc/rtc.c
index b64f63a..e6645b8 100644
--- a/rtc/rtc.c
+++ b/rtc/rtc.c
@@ -221,11 +221,11 @@
 	printf("[%s]: init rtc\n", TAG);
 
 	ret = xInstallRemoteMessageCallbackFeedBack(AOREE_CHANNEL, MBX_CMD_SET_RTC, MboxSetRTC, 0);
-	if (ret == MBOX_CALL_MAX)
+	if (ret)
 		printf("[%s]: mbox cmd 0x%x register fail\n", TAG, MBX_CMD_SET_RTC);
 
 	ret = xInstallRemoteMessageCallbackFeedBack(AOREE_CHANNEL, MBX_CMD_GET_RTC, MboxGetRTC, 1);
-	if (ret == MBOX_CALL_MAX)
+	if (ret)
 		printf("[%s]: mbox cmd 0x%x register fail\n", TAG, MBX_CMD_GET_RTC);
 
 	reboot_mode = get_reboot_mode();